In general, furniture, office desks, cabinets, or industrial rackmount chasses include two parts, respectively: a movable part and a fixed part, and the movable part can be moved with respect to the fixed part for storage or use. Therefore, a conventional three-stage slide rail comprised of an outer rail, a middle rail and an inner rail is adopted to improve the smoothness of the movable components during use, wherein the outer rail is generally fixed to the fixed part, and the inner rail is fixed to the movable part, and the middle rail is coupled between the outer rail and the inner rail by a ball bearing type slide assisting element, so that the inner rail and the middle rail can be pushed or pulled reciprocally in the axial direction with respect to the outer rail in order to pull out or push in the movable part with respect to the fixed part, and such three-stage slide rail can be pulled or pushed to a relatively large extent to achieve the effects of reducing the occupying space significantly for storage, catching the attention of most related manufacturers, and providing a popular useful product.
However, the three-stage slide rail requires an additional linking mechanism in order to fully pull out the middle rail, maintain its fixed status, and pull out the inner rail synchronously in order to obtain the best smoothness and stability of the operation, and such linking mechanism is called “a synchronous mechanism of a slide rail”. Since the middle rail is usually situated at an outermost position where the middle rail is pulled out when the slide rail is fully pulled out, and the fixed status of the middle rail is released while the inner rail is retracted and stored in order to receive the middle rail synchronously. Compared with the using status of a conventional movable part (such as a drawer), the slide rail can just provide a way of pulling out the inner rail and the middle rail synchronously to reduce the load stress produced when pulling out the middle rail to improve the service life of the slide rail only, but it still has the drawback of unable to wait for the inner rail to slide to the top of the middle rail into before restoring its original position synchronously. With such arrangement, a very large torque may be exerted onto the middle rail during the process of pushing in the middle rail, and may even damage the middle rail. Facts show that when the slide rail is damaged, the damage usually occurs at the joint between the middle rail and the inner rail. Therefore, it is a difficult problem for related manufacturers to resume the middle rail and the inner rail to their original positions synchronously.
In view of the aforementioned problem, the disclosure of this disclosure based on years of experience to conduct extensive researches and experiments, and finally developed a synchronous mechanism of a slide rail to obtain a very effective interactive relation by a simple mechanical method to improve the smoothness and stability of the slide rail, so that the slide rail produces become more practical and extensively used in various different products.